Presence services are an emerging technology that provide information of user's availability and capabilities. Such presence services are primarily used for providing availability information of one or more users to another user of a system. This availability information includes an indication of availability or willingness of the user to engage in immediate communication. For example, Microsoft® Live Communication Server (LCS) may be configured to provide availability indicators in desktop computer applications or smart telephony device applications such that a user is provided with availability information of another user, prior to initiating communication, such as making a telephone call.
It is common for users to have multiple contact addresses for real-time voice and multi-media connections. For example, a business person may be reached via his/her business telephone number, cell phone or wireless PDA number, home number or VoIP number. Any of these numbers may appear on the user's business card and may be used to set up synchronous voice connections to the user, but the business card provides no guidance for a caller as to which number is suitable at any particular time. Since calls initiated using some numbers (e.g. home) may be more intrusive than others (e.g. office) a caller must rely on his/her own social and business judgment as to which number to try first. For example, a caller may not hesitate to telephone an individual any time at his/her business number but would be hesitant to call a home number after hours for anything other than an emergency. All of the foregoing give rise to a form of ‘telephone tag’, as callers try one number after another in an attempt to reach the user.
Call Forward Always and Call Forward No Answer are common PBX features that allow a user who will not be available at his/her main business number to forward incoming calls to a more suitable location. Filtering rules may be used to permit calls from certain callers (identify by Caller Line ID) in certain contexts to be forwarded to more appropriate destinations, such as described in United States Patent Application Publication 2005/0100157 dated May 12, 2005, entitled Context Aware Call Handling System. However this requires the called party to program suitable filtering rules.
In SIP systems, it is possible for the called party to send a “redirect” message to the calling party at the time the call is originated. Instead of locally forwarding the call, the called party sends a message containing another address that it wishes the call be redirected to.
It is also known in VoIP and other systems to provide a “one number” feature whereby the user publishes only one number for contact purposes. When that number is called, system logic directs the call to one or more physical numbers that are selected according to the called party's preferences.
Call coverage lists are similar to the “one number” feature whereby a called party programs lists of numbers to which an incoming call can be redirected, either in parallel or sequentially. The sequential call redirection is most common, whereby a list of numbers is provided to which an incoming call is redirected in sequence on the occurrence of no answer on each successive number. Thus a user may set a path starting with his/her desk phone, then his/her cell phone, his/her assistant's phone and finally his/her voicemail.
Call redirection and “one number” features are relatively new to VoIP systems and it will be several years before these systems and their features become common place. Call coverage systems are not supplied by all switch manufactures. Call forwarding relies on the called party to remember to set his forwarding options properly, which is commonly not done.